Redox Reactions - Result Question 14

####14. Consider the change in oxidation state of bromine corresponding to different emf values as shown in the diagram below :

[2018]

BrO41.82VBrO31.5VHBrO

Br1.0652VBr21.595V

Then the species undergoing disproportionation is

(a) BrO3

(b) BrO4

(c) HBrO

(d) Br2

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Solution:

  1. (c) Calculate Ecell  corresponding to each compound undergoing disproportionation reaction. The reaction for which Ecell  comes out +ve is spontaneous.

HBrOBr2E=1.595V,SRP (cathode) HBrOBrO3E=1.5V,SOP (anode) 2HBrOBr2+BrO3Ecell =SRP (cathode) SRP (anode) =1.5951.5=0.095VEcell >0ΔG<0 [spontaneous] 

Reaction in (d) involves comproportionation or synproportionation. When two reactants, each containing the same element but with a different oxidation number, form a product in which the element involved reach the same oxidation number.

It is opposite to disproportionation.

15 .

i.e. maximum change in oxidation number is observed in Cl ( +5 to -1 ).



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